In, for example, an air-conditioning apparatus that uses a refrigeration cycle (heat pump cycle), a refrigerant circuit that circulates a refrigerant is formed by connecting a heat-source-device-side unit (to be also referred to as a heat source device or an outdoor unit hereinafter) including a compressor and a heat-source-device-side heat exchanger, and load-side units (to be also referred to as indoor units hereinafter) including flow control devices (for example, expansion valves) and indoor-unit-side heat exchangers to one another by refrigerant pipes. In the indoor-unit-side heat exchanger, air-conditioning is performed while changing, for example, the pressure and temperature of the refrigerant in the refrigerant circuit, using the fact that the refrigerant receives or transfers heat from or to the air in an air-conditioned space, which is to undergo heat exchange, when the refrigerant evaporates or condenses.
An exemplary air-conditioning apparatus has conventionally been available which is capable of performing a simultaneous cooling and heating operation (cooling and heating mixed operation) in which cooling or heating is performed in each of a plurality of indoor units by automatically determining whether to perform cooling or heating for each indoor unit, in accordance with the temperature set on a remote controller provided to a corresponding indoor unit, and the temperature of the environment surrounding this indoor unit.
In an air-conditioning apparatus to be installed in, for example, a cold climate area, if the temperature of the air on the outside (to be referred to as the outdoor air hereinafter) is low, the refrigerant is guided via an injection pipe into an intermediate portion of a compression stroke of a compressor, provided in a heat source device, so as to improve the heating capacity (see, for example, Patent Literature 1). Such a configuration improves the capacity by increasing the density of refrigerant discharged from the compressor.
Guiding the refrigerant via the injection pipe into the intermediate portion of the compression stroke of the compressor will be referred to as “injection” hereinafter. The heating capacity refers to the amount of heat supplied to the indoor unit per unit time by refrigerant circulation during heating. Likewise, the cooling capacity refers to the amount of heat supplied to the indoor unit per unit time by refrigerant circulation during cooling. The heating capacity and the cooling capacity will sometimes be collectively referred to as “the capacity” hereinafter.